<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <!-- 布局：从整体到局部 -->
    <table border>
        <tr>
            <th>学号</th>
            <th>姓名</th>
            <th>年龄</th>
        </tr>
        <tr>
            <td rowspan="3">1</td>
            <td>2</td>
            <td rowspan="3">3</td>
        </tr>
        <tr>
            <!-- <td>4</td> -->
            <td>5</td>
            
        </tr>
        <tr>
            <!-- <td>4</td> -->
            <td>5</td>
        </tr>
    </table>
    <table border>
        <tr>
            <th colspan="2">1</th>
            <th colspan="2">3</th>
        </tr>
        <tr>
            <th>1</th>
            <th>2</th>
            <th>3</th>
            <th>4</th>
        </tr>
    </table>
</body>
</html>